In Dynamics 365 for Operations (affectionately known as AX7), there is a clear distinction between binary hotfixes and metadata hotfixes (in LCS shown as "binary updates" and "X++ updates"). The product also has monthly platform releases and as of this writing a twice a year application release. I wanted to take a bit of time to explain the details of each and the distinction between them.

To provide context for this post, it's important to note that the product is split in two parts:- Platform: kernel things, and some X++ code that are lower-level; things like batch framework, number sequences, print management, user info, etc.- Application: The actual business logic. Customers, sales orders, production module, etc. Also some binary things like financial reporting (MR) and the SSRS framework for AX.

Platform ReleasesAfter the release of Platform Update 4 (in February 2017), the platform now releases a monthly update. The platform consists of both the lower-level kernel binaries, as well as some X++ packages. However, the platform packages are "sealed" from over-layering, so even though you do get updated X++ code on your development boxes, you don't actually compile or customize these. You can extend them, of course. Each platform release contains any hotfix on the last platform, plus any new features (so they are cumulative - no need to install each one individually, just take the latest). Since this is just platform, the impact on the functionality is extremely minimal. Additionally, any code changes made by developers at Microsoft is checked for breaking changes (which are not allowed). This means the database schema cannot be changed (for the most part) and all APIs (method signatures etc.) should remain the same. This ensures any extensions won't break - the expectation is they don't need to be recompiled (i.e. you update platform, but no need to recompile/redeploy your extension packages). There are also backward compatibility checks to make sure older version of the application can run on newer versions of the platform.In reality this all means that you can compile any code you have on an old platform, and deploy it on an environment with a newer platform - because the runtime is backwards compatible. As a result, many ISVs will develop and build their code on a "common" platform (for example, the fall release 2016 was released on Platform Update 3, and customers can install it on a newer platform (say, platform 7).This also means that there are no individual hotfixes to pick. First, unless a really nasty issues appears, bugfixes will just come in the next month's update. But if there are critical fixes, they will be cumulative - meaning each new hotfix is just a newer build of the same platform; get the latest and you have all hotfixes.

Application ReleasesThe application actually consists of a few different things. Binaries and metadata. Application binaries are considered things like MR, SSRS components for AX, etc. Metadata is considered all the X++ code related to the application (sales orders, customers, etc.).An application release is considered a major or minor version change. For example, the original version of AX7 had application 7.0. The fall release (2016) was 7.1. Spring release in 2017 is 7.2. Note that this is different than the platform - the platform will be backwards compatible, so there's no major or minor release change. An application release then also means it's both the binaries and the metadata combined as one release.

Now, how do you consume these updates and upgrades?

Application Metadata HotfixesSince as of this writing (2017!) you can still over-layer the application code, it means metadata hotfixes come in the form of X++ hotfixes. You have to install the hotfix on a development box, which fixes the existing code - and then you have to build and create a deployable package to actually consume the hotfix somewhere. You can download hotfixes from issue search of the "X++ updates" tile on an environment's page (at the bottom). Since these are just hotfixes, they have no impact on the actual application release you are running. You just have your original release, plus some hotfixes. Since you add those to source control to get built by the build VM, you only install them once and other developers will just synchronize them onto their boxes from source control.

Application Binary HotfixesSince the application is split in metadata as well as binaries, as explained above, you also need binary hotfixes next to the metadata hotfixes. These will be things like hotfixes for MR for example. These can be download from issue search, or also with the next update described. This will change once the application is sealed from over-layering.

Platform UpdatesPlatform updates effectively update your platform as described in the platform release above. A platform update can be download from the global asset library and deployed.

Binary UpdatesOn an environment page, there is also a tile called "Binary Updates". On environments of platform update 4 or newer, this effectively lets you download the latest version of the platform, as well as any application binary hotfixes. Since the tile is a combination of application binary hotfixes as well as platform updates, just installing a platform update from the global asset library (as described above) will not necessarily set the tile counter to 0 (zero) since there may still be applicable application binary hotfixes.

Application UpgradesAs of this writing, an application version is released twice per year (typically spring and fall releases). Since this changes the application functionality, it requires a code upgrade, full testing of the application and customizations, and a data upgrade.